Sensor array package

ABSTRACT

A sensor array package can include a sensor disposed on a first side of a substrate. Signal trenches can be formed along the edges of the substrate and a conductive layer can be deposited in the signal trench and can couple to sensor signal pads. Bond wires can be attached to the conductive layers and can be arranged to be below a surface plane of the sensor. The sensor array package can be embedded in a printed circuit board enabling the bond wires to terminate at other conductors within the printed circuit board.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/640,589, filed Apr. 30, 2012 and entitled “SENSORARRAY PACKAGE” by ARNOLD et al., which is incorporated by reference inits entirety for all purposes.

FIELD OF THE DESCRIBED EMBODIMENTS

The described embodiments relate generally to packaging for sensors, andmore particularly, to low profile sensor array packages.

BACKGROUND

Sensors and sensor arrays can be formed from customized integratedcircuits. Sensor arrays are often used to sense environmentalcharacteristics or can act as a user input for computing devices. Sensorarrays are often formed on a silicon wafer, using similar processingtechniques to those used to fabricate other integrated circuits, such asmemories, processors, field programmable gate arrays (FPGAs) and thelike.

Sensors, unlike some general purpose integrated circuits, can haveunique packaging and mounting requirements. Typical integrated circuits,for example, can have related silicon bonded out, and then packaged. Thebonding out steps can couple signals on the silicon to pins or balls onthe package. The packaging step can include encapsulating the silicondie in a package (typically plastic or ceramic). The packing can supportand protect the otherwise fragile silicon die. However, since sensorsare meant to interface with the environment, the packaging steps areoften different.

Sensors are often outward facing, and generally exposed to a userenvironment. Instead of having the silicon die protected by a package,the die is often times exposed on the surface of a supporting element.While such configurations permit the sensor to function, theseconfigurations can be bulky and can take up a relatively large amount ofvolume, increasing the size of a user device that the sensor isultimately used.

Therefore, what is needed is a sensor, sensors, and/or sensor arrayswhich overcome these and other drawbacks.

SUMMARY OF THE DESCRIBED EMBODIMENTS

One embodiment of a low profile sensor array assembly can include asensor disposed on a first side of a substrate. Signal trenches can alsobe formed on the first side of the substrate and can be near sensorsignal pads and extend to one edge of the substrate. A conductive layercan be deposited in the signal trench and couple to sensor signal pads.Bond wires can attach to the conductive layer and can couple signalsfrom the sensor to external pads.

Another embodiment of a low profile sensor array assembly can include asensor disposed on a first side of a substrate. The substrate caninclude a shaped feature on a first edge positioned near a signal pad ofthe sensor. The shaped feature can be configured to support a wire bondball below a surface plane relative to the sensor. A conductive layercan be deposited on the substrate coupling the signal pad and the wirebond ball. A bond wire can be coupled to the wire bond ball and bearranged to remain below the surface plane relative to the sensor.

According to another embodiment of the invention, a low profileintegrated circuit assembly includes at least one integrated circuit, asubstrate including a first side, wherein the integrated circuit isdisposed on the first side, at least one signal trench, formed on thefirst side of the substrate, proximate to an integrated circuit signalpad and extending to one edge of the substrate, a conductive layerdisposed in the signal trench and coupling to the integrated circuitsignal pad, and a bond wire configured to couple the conductive layer toan external pad wherein the bond wire, signal trench and conductivelayer are maintained below a surface plane of the integrated circuit.

According to another embodiment of the invention, a low profile circuitassembly includes an integrated circuit, a substrate including a firstside, wherein the integrated circuit is disposed on the first side, ashaped feature on a first edge of the substrate disposed proximate to anintegrated circuit signal pad and arranged to support a wire bond ballbelow a surface plane of the integrated circuit, a conductive layerdisposed on the first side of the substrate and configured to couple theintegrated circuit signal pad to the wire bond ball, and a bond wirecoupled to the wire bond ball and configured to remain below the surfaceplane of the integrated circuit.

According to another embodiment of the invention, a low profile assemblyincludes a first substrate, a second substrate, larger than the firstsubstrate, wherein the first substrate is disposed on a first side ofthe second substrate, and at least one signal trench disposed on thefirst side of the second substrate and configured to support bond wiresconnections to the first substrate below a surface plane of the firstsubstrate.

According to another embodiment of the invention, a method of forming alow profile assembly includes forming at least one signal trench in asubstrate, depositing a barrier layer over the substrate proximate theat least one signal trench, depositing a seed layer of metal in the atleast one signal trench, masking the substrate, barrier layer, and atleast one signal trench, depositing additional metal over the maskedsubstrate, and removing the mask and seed layer to form a finalconductive layer in the at least one signal trench.

Other aspects and advantages of the invention will become apparent fromthe following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the described embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings. These drawings in no waylimit any changes in form and detail that may be made to the describedembodiments by one skilled in the art without departing from the spiritand scope of the described embodiments.

FIGS. 1A and 1B are simplified diagrams of a low profile sensor, inaccordance with one embodiment of the invention.

FIGS. 2A-2D illustrate side views of exemplary embodiments of a lowprofile sensor.

FIGS. 3A-3D illustrate possible shape profiles for signal trenches.

FIGS. 4A-4G illustrate steps that can be used to form a signal trench.

FIG. 5 is a flow chart of method steps for forming signal trenches in asubstrate.

FIG. 6 is a side view of signal trench, in accordance with oneembodiment of the specification.

FIG. 7 shows another embodiment of a low profile sensor.

FIG. 8 shows a side view of one embodiment of a way of forming multiplelow profile sensors.

FIG. 9 illustrates optional features that can be applied to a lowprofile sensor assembly embedded in a PCB.

FIGS. 10A and 10B illustrate another embodiment of a low profile sensor.

FIGS. 11A-11E illustrate steps that can be used to mount a low profilesensor on a substrate.

FIG. 12 is a flow chart of method steps for mounting a low profilesensor on a substrate.

FIG. 13 is a top view of yet another embodiment of a low profile sensor.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

Representative applications of methods and apparatus according to thepresent application are described in this section. These examples arebeing provided solely to add context and aid in the understanding of thedescribed embodiments. It will thus be apparent to one skilled in theart that the described embodiments may be practiced without some or allof these specific details. In other instances, well known process stepshave not been described in detail in order to avoid unnecessarilyobscuring the described embodiments. Other applications are possible,such that the following examples should not be taken as limiting.

In the following detailed description, references are made to theaccompanying drawings, which form a part of the description and in whichare shown, by way of illustration, specific embodiments in accordancewith the described embodiments. Although these embodiments are describedin sufficient detail to enable one skilled in the art to practice thedescribed embodiments, it is understood that these examples are notlimiting; such that other embodiments may be used, and changes may bemade without departing from the spirit and scope of the describedembodiments.

Sensors and sensor arrays are often fabricated on a silicon die and thensupported with a structure underneath the die. To protect the surface ofthe sensor, often a clear cover is applied. However, some embodimentsrequire little if any cover over the sensor, to increase sensorsensitivity. Furthermore, the support structure can be bulky and in turnincrease the size of a product design including the sensor.

One embodiment of a low profile sensor can include a sensor disposed ona silicon die. The silicon die, in turn, can be embedded in a printedcircuit board (PCB) structure. The low profile sensor can include signaltrenches formed in the silicon to allow bond wires to couple to thesensor, while remaining substantially below a surface plane of thesensor. Bond wires can couple the sensor directly to other embeddeddevices, or to one or more conductive layers in the PCB.

Signal trenches can be formed by removing substrate material such aswith a saw or grinder, or signal trenches can be formed by selectivelyetching the substrate. After forming the signal trench, a conductivematerial can be deposited into the trench forming a conductive pathbetween a sensor pad and the trench. Finally, a bond wire can beattached to the conductive material and can be used to couple signalsfrom the sensor to external devices or other components.

FIGS. 1A and 1B are simplified diagrams of a low profile sensor 100, inaccordance with one embodiment of the specification. FIG. 1A shows a topview of the low profile sensor 100. Low profile sensor 100 can include asubstrate 102 and a sensor 104 disposed on a first surface of substrate102. Substrate 102 can be silicon or any other technically feasiblematerial such as gallium arsenide, gallium nitride or the like. Sensor104 can be a single sensor or an array of sensors. Sensor 104 can beused to detect user input such a touch (pressure), heat or capacitivesensor. In other embodiments, sensor 104 can be any other feasibleintegrated circuit. Such integrated circuits can be formed on anytechnically feasible substrate such as silicon, gallium arsenide or thelike. In other words, the mounting techniques described herein can beapplied equally to any integrated circuit, not only sensors. Throughoutthis specification, reference will be made to a sensor in thedescription, but it is understood that any integrated circuit can besubstituted for the sensor. Also disposed on the first surface are pads106 that can be electrically coupled to signals in sensor 104. FIG. 1Aalso shows a top view of a signal trench 108. A layer of metal 110 (orother conductor) can be deposited in signal trench 108 and couple to pad106. This is described in greater detail below in conjunction with FIG.4. FIG. 1B is a side view of low profile sensor 100. This view showssome detail of a possible shape of signal trench 108 within substrate102. The shape of the signal trench 108 is indicated with dashed lines.

FIGS. 2A-2D illustrate side views of exemplary embodiments of a lowprofile sensor. FIGS. 2A and 2B shown low profile sensor 100 embedded ina PCB. FIGS. 2C and 2D show low profile sensor 100 mounted on thinsubstrate, such as a flex circuit. These figures are not drawn to scale,but are meant to show relationships between low profile sensor 100 andPCB or low profile sensor 100 and thin substrate. These figures are notmeant to be exhaustive and show every possible configuration, but ratherillustrate exemplary approaches. Persons skilled in the art canappreciate that other approaches exist. FIG. 2A illustrates a firstbonding approach 200 between substrate 102 and PCB 204. Substrate 102can include a sensor 104 disposed on a first side. Signal trenches 215are shown in side view. Metal layer 110 can be formed in signal trenches215 and can couple to pad 106. Wire bond 208 can couple metal layer 110to a pad 210 that can be on any layer within PCB 204. Wire bonds 208 canbe implemented to be below the surface plane 220 of sensor 104. Asurface plane can be an imaginary plane that extends in all directionsand is co-planar with the highest surface of sensor 104. Surface plane220 is denoted with a dashed line.

FIG. 2B illustrates a second bonding approach 250 between substrate 102and PCB 204. Sensor 104 is mounted on substrate 102 and includes pad106. Signal trenches 215 can be formed in substrate 102 and can includemetal layer 110 coupled to pad 106. Substrate 102 and separate device252 can be embedded together in PCB 204. In some embodiments, two ormore separate devices 252 can be embedded in PCB 204. Device 252 can bea separate integrated circuit that can be used to provide additionalfunctionality to sensor 104. For example, device 252 can be a signalprocessing device used to preprocess signals from sensor 104. Device 252can include at least one pad 254 to couple to signals within device 252.Wire bond 208 can couple metal layer 110 to device 252. Wire bond 208can be maintained below surface plane 220.

FIG. 2C illustrates a third bonding approach 260 between substrate 102and thin substrate 225. In one embodiment, thin substrate 225 can be aflexible circuit (flex circuit). Substrate 102 can be affixed to thinsubstrate 225 with an adhesive, such as a glue, epoxy or tape adhesive.Sensor 104 can be disposed on substrate 102. Signal trenches 215 can beformed on substrate 102 and can support metal layer 110 over pad 106. Abond wire 208 can couple metal layer 110 to a pad 210. In thisembodiment, wire bond 208 can be maintained below surface plane 220.

FIG. 2D illustrates a fourth bonding approach 270 between multiplesubstrates and thin substrate 225. As shown, a first substrate 102A anda second substrate 102B are affixed to thin substrate 225. Bond wire 208can be used to couple metal layers 110 from two or more substrates. InFIG. 2D, bond wire 208 can couple signals from first substrate 102A tosecond substrate 102B. In this manner, two or more substrates 102A, 102Bcan be linked together.

FIGS. 3A-3D illustrate possible shape profiles for signal trench 215. Inone embodiment, the shape profile of the signal trench can affect signalintegrity of the signals carried within the signal trenches 215. Forexample, some common metal deposition techniques (i.e., filamentevaporation or electron beam evaporation) can have poor coverage onvertical or near vertical surfaces Other metal deposition techniques canhave improved coverage on vertical or near vertical surfaces, but mayhave other associated costs (i.e., sputter deposition). In other words,certain shape profiles can be preferred over others depending on aselected metal deposition method. Other shape profiles can be possiblebeyond the exemplary shapes described below.

FIG. 3A illustrates a vertical profile 301 for signal trench 215. Inthis embodiment, trench 215 can have a substantially rectilinear profile301. The rectilinear profile 310 can be formed by many methods,including saw blade and deep reactive ion etch techniques. In someembodiments, two or more shaping methods can be combined to createvertical profile 301. As shown, vertical profile 301 can include atleast one substantially vertical section 302. In some embodiments,vertical or near vertical sections may not have relatively even metalcoverage. An uneven metal layer can include voids or otherirregularities that could result in a discontinuity in the metal.

FIG. 3B illustrates a ramp profile 303 for signal trench 215. The rampprofile 303 can be formed a number of ways. In one embodiment a sawblade can be used to form and shape signal trench 215. In anotherembodiment, ramp profile 303 can be formed, at least in part, by wetetching with potassium hydroxide (KOH). Etching with potassium hydroxidecan have the advantage that, by virtue of the reactant, a ramp angle isnaturally produced. One advantage of ramp profile 303 is that theprofile includes no substantially vertical portions. Thus, the shape ofthe profile can enable the deposition of relatively even metal layers110.

FIG. 3C illustrates an engineered curve profile 305. Engineered curveprofile 305 can be formed with a shaped saw blade, or by etching. Insome embodiments, two or more shaping methods can be combined to createengineered curve profile 305. One advantage of engineered curve profile305 is that the profile does not include any sharp bends or curves.Sharp bends or curves can become stress points within the substrate 102.These stress points can become starting points for fractures and cracks.Another advantage of engineered curve profile 305 is that the profiledoes not include any substantially vertical portions, therefore theprofile can support the formation of relatively even metal layers.

FIG. 3D illustrates a bowl shaped profile 307. This profile can beformed with a saw or with etching methods. One advantage of the bowlshaped profile 307 is the inherent strength of the profile. Substratearea near bowl shaped profile 307 can be relatively stronger whencompared to areas near other profiles such as rectilinear profile 303. Adrawback of the bowl shaped profile 307 it that it can include arelatively vertical region 308. As described above, vertical regions candevelop discontinuities and voids when certain metal depositiontechniques are used.

FIGS. 4A-4G illustrate steps that can be used to form signal trench 215.These illustrations are cross sectional views of the trench, with thesurrounding areas not drawn to clarify the drawing. FIG. 4A shows apossible beginning state including substrate 102. Pad 106 and sensor 104are disposed on a first side of substrate 102. FIG. 4B shows substrate102 with signal trench 215 formed into the substrate 102. Sensor 104 andpad 106 remain on the surface of substrate 102. Signal trench 215 can beformed in the shape of any technically feasible profile. Exemplaryprofiles are described above in FIG. 3. Ramp profile 303 is selected asthe exemplary profile in this figure. Ramp profile 303 can be formedusing a potassium hydroxide etch process, for example. FIG. 4C shows abarrier layer 405 deposited on the substrate 102. In one embodiment,barrier layer 405 can be formed with techniques similar to formingpassivation layers. In one embodiment, barrier layer 405 can helpprotect sensor 104.

FIG. 4D shows substrate 102, pad 106 and sensor 104. In this view, ametal seed layer 410 has been deposited over the substrate 102, barrierlayer 405 and pad 106. As shown, seed layer 410 can be deposited in theregions of the signal trench 215 where a final conductive channel isdesired. In one embodiment, seed layer 410 can be deposited bysputtering a conductive metal, such as aluminum. FIG. 4E shows substrate102, pad 106 and sensor 104 with a mask 415 selectively applied to thefirst surface. Mask 415 can be used to define regions where additionalmetal can be deposited over the seed layer 410. In one embodiment mask415 can be a liquid photoimageable mask. FIG. 4F shows metal 420deposited over substrate 102, pad 106, seed layer 410 and mask 415.During the metal deposition process, metal can be non-selectivelydeposited over the entire substrate 102. In FIG. 4G shows substrate 102after the mask 415 and excess metal seed layer 410 is removed. In oneembodiment, metal seed layer 410 can be removed with a wet etch process.Removal of the mask 415 and metal seed layer 410 can define the finalshape of the metal layer 420 in signal trench 215.

FIG. 5 is a flow chart of method steps for forming signal trenches 215in a substrate 102. The method begins in step 502 where the trenchprofile is formed in the substrate. The trench profile can be selectedfrom one of the profiles described in FIG. 3, or any other technicallyfeasible profile. In step 504, a barrier layer can be formed anddeposited over the substrate 102. The barrier layer can help protect thesubstrate 102 after trenches are formed in substrate 102. In step 506, aseed layer of metal can be deposited in the formed trench and can coupleto the pad 106. In step 508, a mask can be selectively placed on thesubstrate. In one embodiment, the mask can be a liquid photoimageablemask. The mask 405 can be used to determine the areas on the substrate102 where the metal within the signal trench 215 will be positioned. Instep 510, additional metal can be deposited over substrate 102. In oneembodiment, metal can be sputtered. In step 512, the mask 405 and excessseed layer can be removed, forming the final conductive layer in thesignal trench and the method ends.

Formation of the signal trenches 212 can provide access to signals fromsensor 104 while maintaining connections below the surface plane 220 ofsensor 104. In order to fan out the signals to other devices, wires canbe bonded to the metal deposited in the signal trenches 215. After awire is bonded, the wire can be routed to a pad or other conductor. Carecan be taken to maintain the path of the wire to be below the surfaceplane 220 of sensor 104, thereby allowing a low profile mounting of thesensor 104 and substrate 102. In one embodiment, a wire bond 208 can beformed by depositing a wire bond ball in the signal trench 215 on metallayer 206. The wire can be guided within the signal trench 215.

FIG. 6 is a side view 600 of signal trench 215, in accordance with oneembodiment of the specification. The side view 600 includes substrate102, pad 106 and metal layer 110. Depth 602 of signal trench 205 can bea function of the elements that can be included within signal trench215. Wire bond ball 604 can be bonded to metal layer 110 in the bottomof signal trench 215. The height 606 of wire bond ball 604 can vary.Common heights can range from 5-15 μm. Diameter 608 of wire can vary byapplication; current carrying wires (power) can be thicker than wiresonly carrying signals. A typical wire diameter 608 can be 25 μm.Finally, bend radius 610 can affect the depth 602. In one embodimentdepth 602 can be determined, at least in part by the sum of the wirebond ball height 606 plus wire diameter 608 plus bend radius 610.

The width 612 of the bottom of signal trench 215 can be determined, atleast in part, by elements that are included in the bottom of the signaltrench 215. A typical diameter 615 of wire bond ball can be 50 μm. Thedistance 617 from the wire bond ball to the edge of the substrate 102can be 20 μm. This distance can be reduced, however, since edge chippingcan occur, yield of the device can be reduced if the distance is reducedtoo much. The distance 618 from the wire bond ball to the inside edge ofthe bottom of signal trench 15 can be between 5 to 10 μm. In someembodiments, the distance 618 can be influenced by a tool used for wirebonding. Thus, in one embodiment, width 612 can be determined, at leastin part, by the sum of wire bond ball diameter 615, plus distance tosubstrate edge 617 plus distance to inside edge 618.

FIG. 7 shows another embodiment of a low profile sensor 700. In thisembodiment, signal trenches 215 can be replaced by shaped featuresdisposed on the edge of the substrate. Substrate 702 includes pad 106disposed on a first side of substrate 702. Shaped feature 706 can beformed on one corner of substrate 702. Metal layer 704 can be disposedon pad 106 and can also be disposed on shaped feature 706. Wire bondball 604 can be positioned on shaped feature 706 such that wire 708 canbe maintained below surface plane 220 of sensor 104.

FIG. 8 shows a side view 800 of one embodiment of a way of formingmultiple low profile sensors. Multiple low profile sensors can be formedon a silicon wafer with each individual low profile sensor formed on anindividual die on the wafer. Prior to separating the individual dice, agrinding wheel 802 or shaped saw blade can form signal trenches 215across two or more dice, with a relatively continuous grind or cut. Inthe example shown in FIG. 8, grinding wheel 802 can form signal trenches215 in first and second low profile sensors 805 and 807 respectively. Ina later operation, a saw can separate the dice forming a saw cut 810.

FIG. 9 illustrates optional features that can be applied to a lowprofile sensor assembly 901 embedded in a PCB 204. The low profilesensor assembly 901 can include sensor 104 and substrate 102. After thelow profile sensor assembly 901 is embedded in PCB 204, empty voids 902,especially in the areas of signal trench 215, can be filled with anepoxy, resin or other like material to strengthen the bond between lowprofile sensor assembly 901 and PCB 204 and form a relatively planarsurface. In another embodiment, components 904 can be disposed on PCB204, on the side facing away from sensor 104. Components 904 can bepassive components such as resistors, inductors, capacitors or the like.Components 904 can be coupled to sensor 104 or other devices.

FIGS. 10A and 10B illustrate another embodiment of a low profile sensor1000. In this embodiment, individual signal trenches can be replacedwith a single trench 1010 that can be formed on edge of substrate 102.Sensor 104 can be disposed on one surface of substrate 102. Pad 106 canbe disposed on the same planar surface as sensor 104. Metal layer 1015can couple pad 106 to at least one region of single trench 1010. Inanother embodiment, pads can be positioned within single trench 1010region as shown with pad 1020. Metal layer 1025 can be deposited overpad 1020 and be positioned in single trench 1010. FIG. 10B shows a sideview of low profile sensor 1000. Pad 106 is shown planar to sensor 104.Metal layer 1015 can be deposited on pad 106 and into single trench1010. In another embodiment, pad 1020 can be positioned in single trench1010. Metal layer 1025 can be deposited on pad 1020 and into singletrench 1010.

FIGS. 11A-11E illustrate steps that can be used to mount a low profilesensor on a substrate. In one embodiment, the substrate can be a thinsubstrate 1110, such as a flexible cable. FIG. 11A shows an initialstate of thin substrate 1110 and pads 1120. Adhesive 1130 can bedeposited on thin substrate 1110. Adhesive 1130 can be an epoxy, glue,adhesive tape or other similar article. In FIG. 11B, substrate 1140including sensor 1145 can be positioned on adhesive 1130. In FIG. 11C,wire bond balls 1150 can be attached to substrate 1140 in preparationfor bond wire attachment. In FIG. 11D, bond wires 1160 can be attachedto wire bond balls 1150 and can couple signals from sensor 1145 to pad1120. In one embodiment, optional wire bond balls 1165 can be coupled topad 1120. In FIG. 11E bond wires 1160 can be encapsulated to protectthem in an epoxy 1170, resin or similar material.

FIG. 12 is a flow chart of method steps for mounting a low profilesensor on a substrate. In one embodiment, the substrate can be a thinsubstrate such as a flexible circuit. The method begins in step 1210where an adhesive is applied to a substrate. The adhesive can be aliquid adhesive such as an epoxy or can be a tape based adhesive. Instep 1220, the sensor/substrate combination can be bonded to thesubstrate. In step 1230, bond wire balls can be attached to thesubstrate. In one embodiment, the bond wire balls can be coupled tometal layers on the substrate enabling access to the signals in thesensor. In step 1240, bond wires can be attached to bond wire balls andpads disposed on the substrate. In step 1250, bond wires can beencapsulated. Encapsulation can help protect fragile bond wires fromdamage.

FIG. 13 is a top view of yet another embodiment of a low profile sensor1300. This embodiment can include both individual single trenches asdescribed in FIG. 1 and multiple signal trenches that can include morethan one signal as described in FIG. 10. Low profile sensor 1300 caninclude substrate 102 and sensor 104. Pads 106 can be disposed outsideof a trench. For example, pad 106 is disposed beyond multiple signaltrench 1310 and beyond single signal trench 1311. In another embodiment,the pad can be disposed inside the trench region. For example, pad 1020can be disposed within multiple signal trench 1310 or within singletrench 1311. Metal layers 1015 can couple to pads 106 beyond signaltrenches 1310 and 1311. Alternatively, metal layers 1025 can couple topads 1020 within signal trenches 1310 and 1311. In some embodiments,multiple signal trenches 1310 can provide greater signal densities,while in some embodiments, single signal trenches 1311 can providegreater strength to substrate 102. Low profile sensor 1300 can possesadvantages of both the signal and multiple signal trench systems.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination.Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer readable code ona computer readable medium for controlling manufacturing operations oras computer readable code on a computer readable medium for controllinga manufacturing line. The computer readable medium is any data storagedevice that can store data which can thereafter be read by a computersystem. Examples of the computer readable medium include read-onlymemory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, andoptical data storage devices. The computer readable medium can also bedistributed over network-coupled computer systems so that the computerreadable code is stored and executed in a distributed fashion.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of specific embodimentsare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the described embodiments to theprecise forms disclosed. It will be apparent to one of ordinary skill inthe art that many modifications and variations are possible in view ofthe above teachings.

1. A low profile integrated circuit assembly, the assembly comprising:at least one integrated circuit; a substrate including a first side,wherein the integrated circuit is disposed on the first side; at leastone signal trench formed on the first side of the substrate, proximateto an integrated circuit signal pad and extending to one edge of thesubstrate; a conductive layer disposed in the signal trench and couplingto the integrated circuit signal pad; and a bond wire configured tocouple the conductive layer to an external pad wherein the bond wire,signal trench and conductive layer are maintained below a surface planeof the integrated circuit.
 2. The assembly of claim 1, wherein the atleast one signal trench is configured to have a ramp profile.
 3. Theassembly of claim 2, wherein the bond wire is further configured toattach to a slope portion of the ramp profile.
 4. The assembly of claim1, wherein the at least one integrated circuit is a sensor.
 5. Theassembly of claim 2, further comprising a flexible printed circuitassembly configured to bond to a second side of the substrate, thesecond side being disposed opposite the first side.
 6. The assembly ofclaim 1, wherein the at least one signal trench includes at least twobond wires configured to couple conductive layers to external padswherein the bond wires, signal trench and conductive layers aremaintained below a surface plane of the integrated circuit.
 7. A lowprofile circuit assembly, the assembly comprising: an integratedcircuit; a substrate including a first side, wherein the integratedcircuit is disposed on the first side; a shaped feature on a first edgeof the substrate disposed proximate to an integrated circuit signal padand arranged to support a wire bond ball below a surface plane of theintegrated circuit; a conductive layer disposed on the first side of thesubstrate and configured to couple the integrated circuit signal pad tothe wire bond ball; and a bond wire coupled to the wire bond ball andconfigured to remain below the surface plane of the integrated circuit.8. The assembly of claim 7, wherein the shaped feature is configured tohave a ramp profile.
 9. The assembly of claim 8, wherein the bond wireis further configured to attach to a slope portion of the ramp profile.10. The assembly of claim 7, wherein the integrated circuit is a sensor.11. The assembly of claim 8, further comprising a flexible printedcircuit assembly configured to bond to a second side of the substrate,the second side being disposed opposite the first side.
 12. The assemblyof claim 7, wherein the shaped feature includes at least two bond wiresconfigured to couple conductive layers to external pads, wherein thebond wires, shaped feature, and conductive layers are maintained below asurface plane of the integrated circuit.
 13. A low profile assembly,comprising: a first substrate; a second substrate, larger than the firstsubstrate, wherein the first substrate is disposed on a first side ofthe second substrate; and at least one signal trench disposed on thefirst side of the second substrate and configured to support bond wiresconnections to the first substrate below a surface plane of the firstsubstrate.
 14. The assembly of claim 13, wherein the at least one signaltrench is configured to have a ramp profile.
 15. The assembly of claim14, wherein the bond wire is further configured to attach to a slopeportion of the ramp profile.
 16. The assembly of claim 13, furthercomprising at least one integrated circuit disposed on the firstsubstrate.
 17. The assembly of claim 14, further comprising a flexibleprinted circuit assembly configured to bond to a second side of thesecond substrate, the second side being disposed opposite the firstside.
 18. The assembly of claim 13, wherein the at least one signaltrench can include at least two bond wires configured to coupleconductive layers to external pads.
 19. A method of forming a lowprofile assembly, comprising: forming at least one signal trench in asubstrate; depositing a barrier layer over the substrate proximate theat least one signal trench; depositing a seed layer of metal in the atleast one signal trench; masking the substrate, barrier layer, and atleast one signal trench; depositing additional metal over the maskedsubstrate; and removing the mask and seed layer to form a finalconductive layer in the at least one signal trench.
 20. The method ofclaim 19, wherein the barrier layer is configured to protect areas ofthe substrate proximate the at least one signal trench.
 21. The methodof claim 19, wherein masking the substrate comprises applying a liquidphotoimageable mask over the substrate, barrier layer, and at least onesignal trench.
 22. The method of claim 21, wherein the appliedphotoimageable mask is configured to define areas on the substratewherein metal within the at least one signal trench is positioned. 23.The method of claim 22, wherein depositing additional metal comprisessputtering metal on the defined areas.
 24. The assembly of claim 1,further comprising a barrier layer overlapping at least a portion of theintegrated circuit.
 25. The assembly of claim 1, further comprising ametal seed layer overlapping at least a portion of the substrate, atleast a portion of the barrier layer, and at least a portion of theconductive layer.